Ink jet print heads have a need for frequent cleaning and capping to avoid clogged nozzles. If the nozzles are not used frequently, ink in the nozzles will dry out and slowly build up until a clog occurs in the nozzle. Customarily manufacturers use a combination of spitting ink (periodically ejecting ink from the print head while in a cleaning station), suctioning ink from the head through the nozzles, and/or capping off of the nozzles to prevent clogs and nozzle dry-up. These measures are often not successful and hardening of ink in the nozzles after a long delay between printing times results in clogged non-functioning nozzles.
It is known to add a moistening device in the print head to keep the nozzle plate moist and thereby prevent ink from drying. For example, see U.S. Pat. No. 4,417,259, issued Nov. 22, 1983, to Maeda, which uses an air cell in the front of the print head that is filled with air during printing, but is filled with a liquid when the inkjet print head is not printing. Another approach to cleaning an ink jet print head in an ink jet printer is to intermittently suck a cleaning solution into the ink jet print head through the nozzles and discharge the solution therefrom, thereby removing hardened ink from nozzles. For example, see U.S. Pat. No. 5,495,272, issued Feb. 27, 1996, to Yamaguchi. It is also known to provide a vapor chamber for enclosing the ink jet nozzles during shutdown periods to prevent ink from drying at the nozzles. See U.S. Pat. No. 3,839,721, issued Oct. 1, 1974, to Chen et al. Many of these prior art systems involve additional cost and complexity of extra tubing and check valves to perform this task, and none have proven to be entirely satisfactory.
It is also known to provide a steam cleaning device that is used to clean the nozzles of ink jet print heads that are being recycled. See U.S. Pat. No. 5,790,147, issued Aug. 4, 1998, to Hensel. However, it is not considered to be practical or safe to employ live steam in an ink jet printer. There is a need therefore for an improved method of cleaning and capping an ink jet print head in an ink jet printer.